Abstract This project consists of the continued development of a unique implantable ischemia monitor that uses subcutaneous sensors in the patient's torso to detect the onset of acute myocardial infarction (AMI). Upon detecting a heart attack, the monitor generates an alarm, which enables the patient to promptly seek medical treatment. In the United States, the median symptom-to-hospital time is 2.4 hours. Lengthy delays between symptom onset and a patient's arrival at a hospital cause both substantial heart tissue damage and many deaths. Approximately 50% of heart attack patients have either atypical or no symptoms at all, causing significant delays in treatment. Each 30 minute reduction of treatment delay provides a 7.5% decrease in mortality and 8.7% decrease in the incidence of congestive heart failure. Prompt treatment of AMIs enabled by real-time ischemia monitoring and alerting will save lives and decrease morbidity. This Phase IIB development builds upon our successful Phase II work, which entailed the creation of prototype implantable cardiac ischemia detection monitors that utilize subcutaneous electrodes, and evaluation of the monitor's algorithm using a target patient population. This Phase IIB project will result in the completion o in vivo safety testing of the subcutaneous monitor that will serve as the basis for obtaining regulatory approval from the United States Food and Drug Administration (FDA). This goal will be realized by achieving the following aims: Aim 1. The primary objective of this aim is to finaliz development of the monitor and evaluate the ability of the subcutaneous monitor to detect and record acute ischemic events in an ambulatory porcine model. The secondary objective of this aim is to evaluate the subcutaneous system's function and safety under normal implantation conditions, without occlusion of a coronary artery. These objectives will be demonstrated by performing a good laboratory practices (GLP) study using juvenile farm pigs. Study results will provide data that supports the safety and potential efficacy of implantation of the subcutaneous system in human subjects. Aim 2. The primary objective of this aim is to demonstrate the safety and efficacy of the subcutaneous system in man. This objective will be demonstrated by performing an FDA approved 180 day study involving approximately 30 subjects. The target population will be high risk patients that are scheduled to receive a stent. The subcutaneous device will be implanted before stent implantation. The deployment of the stent would then be captured by the implanted subcutaneous device to demonstrate ability to detect acute coronary arterial occlusion. The subjects will then be closely followed for 180 days to assess safety and overall performance of the implanted device. Study results would provide data that supports the safety and efficacy of the subcutaneous system and would form the basis of a 510(k) application to the FDA for marketing approval of the subcutaneous system.